Process for preparing high molecular weight sulfonic acids

ABSTRACT

THIS DISCLOSURE CONCERNS A PROCESS FOR PREPARING HIGHPURITY HIGH MOLECULAR WEIGHT SULFONIC ACIDS FROM A PETROLEUM FRACTION (E.G., BRIGHT STOCK). BRIEFLY, THE PROCESS COMPRISES THE STEPS OF: (1) SULFONATING THE PETROLEUM FRACTION, (2) ADDING TO THE SULFONATION MASS, WATER AND A VOLATILE HYDROCARBON SOLVENT (E.G., HEXANE), (3) ALLOWING THE ADMIXTURE TO SETTLE, (4) WITHDRAWING THE AQUEOUS LAYER, AND (5) THEREUPON OBTAINING A SOLUTION OF THE SULFONIC ACIDS. A SALIENT FEATURE OF THE PROCESS IS THE USE OF BOTH WATER AND THE VOLATILE HYDROCARBON SOLVENT. IF DESIRED, IN ORDER TO REDUCE SETTLING TIME, A LOW MOLECULAR WEIGHT SULFONIC ACID CAN BE ADDED TO THE ADMIXTURE OF SULFONATION MASS, WATER AND VOLATILE HYDROCARBON SOLVENT. THE LOW MOLECULAR WEIGHT SULFONIC ACID CAN BE FORMED IS SITU BY INCLUDING A SUITABLE SULFONATABLE HYDROCARBON IN THE PETROLEUM FRACTION SUBJECTED TO SULFONATION.

United States Patent Ofice Patented Mar. 19, 1974 3,798,261 PROCESS FOR PREPARING HIGH MOLECULAR WEIGHT SULFONIC ACIDS Paul C. Kemp, Ponca City, Okla., assignor to Continental Company, Ponca City, Okla. No Drawing. Filed Aug. 26, 1968, Ser. No. 755,446 Int. Cl. C07c 143/00 U.S. Cl. 260-504 R 15 Claims ABSTRACT OF THE DISCLOSURE This disclosure concerns a process for preparing highpurity, high molecular weight sulfonic acids from a petroleum fraction (e.g., bright stock). Briefly, the process comprises the steps of: (1) sulfonating the petroleum fraction, (2) adding to the sulfonation mass, water and a volatile hydrocarbon solvent (e.g., hexane), (3) allowing the admixture to settle, (4) withdrawing the aqueous layer, and (5) thereupon obtaining a solution of the sulfonic acids.

A salient feature of the process is the use of both water and the volatile hydrocarbon solvent.

If desired, in order to reduce settling time, a low molecular weight sulfonic acid can be added to the admixture of sulfonation mass, water and volatile hydrocarbon solvent. The low molecular weight sulfonic acid can be formed in situ by including a suitable sulfonatable hydrocarbon in the petroleum fraction subjected to sulfonation.

BACKGROUND Oil-soluble, metal petroleum sulfonates have been used in lubricating oils for many years. They are particularly useful in imparting detergent properties to the oils. Originally, the natural (or, as commonly known, mahogany) sulfonic acids were obtained by treating an unrefined, relatively low molecular weight (e.g., 300-500) petroleum fraction with a sulfonating agent. Usually, they were a byproduct of the manufacture of white oils.

More recently, it has been found that the oil-soluble, metal petroleum sulfonates obtained by sulfonating a high molecular weight petroleum fraction (e.g., bright stock) are particularly useful in lubricating oils. Lubrication oils containing these high molecular Weight metal sulfonates are particularly useful as detergents in lubricating oils used in stop-and-go driving. Quite frequently, stop-and-go driving in cold weather has a tendency to produce sludge in a lubricating system. The foregoing-described metal sulfonates are useful in combatting this problem.

The production of sulfonic acids from high molecular weight petroleum fractions is entirely difierent from the production of sulfonic acids from low molecular weight petroleum fractions. For example, sulfonation of the low molecular weight fraction produces a phase separation and the sulfuric acid sludge can be removed by settling or centrifuging. Moreover, it is a relatively simple matter to isolate and purify the sulfonic acids by neutralization with an alkali base followed by extraction of the sulfonate from the unsulfonated oil with aqueous alcohol. On the other hand, sulfonation of the high molecular weight fraction produces no phase separation and the removal of excess sulfonating agent presents a problem. Conventional methods of water washing result in the formation of stable emulsions.

My invention concerns a relatively simple process for obtaining high purity sulfonic acids from high molecular weight petroleum fractions.

PRIOR ART The following references are believed to be the most pertinent to the present invention: a

U.S. Pat. No. 2,909,563 teaches the preparation of high molecular weight natural sulfonic acids by a process which uses at least 3 volumes of water per volume of sulfonic acid-oil phase.

U.S. Pat. No. 2,940,994 teaches a sulfonation process which uses a combination of n-hexane and dimethyl sulfoxide to remove the excess sulfuric acid from the sulfonation mass.

U.S. Pat. No. 2,865,957 teaches removal of the spent acid from the sulfonation mass by use of a combination of 50 to 98 percent sulfuric acid and hexane.

Both U.S. Pat. Nos. 2,068,847 and 2,418,784 teach adding a small amount of an aromatic hydrocarbon (e.g., benzene) to the petroleum oil subjected to sulfonation. Neither patent, however, teaches that this feature results in rapid separation of the aqueous and hexane phase.

' It is apparent from the above description that the prior art does not teach a process using a combination of vo1atile hydrocarbon solvent and water. Neither does the prior art teach the combination of volatile hydrocarbon solvent, water, and low molecular weight sulfonic acid.

"BRIEF DESCRIPTION OF THE INVENTION Broadlystated, the present inventionconcerns a process for preparing high-purity, high molecular weight sulfonic acids from a sulfonatable petroleum fraction, wherein the process comprises:

( 1) adding from about 0.2 to about 0.6 part of sulfonating agent to one part of a sulfonatable petroleum fraction, (2) adding to the sulfonation mass of step (1):

(a) from about 0.15 to about 2 parts of water per part of sulfonatable petroleum fraction, (b) from about 0.5 to about 1.5 parts of volatile hydrocarbon solvent per part of sulfonatable petroleum fraction,

(3) allowing the admixture of step (2) to stratify, thereby forming an aqueous phase and a volatile hydrocarbon phase,

(4) withdrawing the aqueous layer, and

(5) thereupon obtaining a volatile hydrocarbon solution of the high combining weight sulfonic acids.

(1) forming an admixture comprising from about 90 to about 99 weight percent sulfonatable petroleum fraction and from about 1 to about 10 weight percent low molecular weight aromatic compound,

(2) adding to the admixture of step 1) from about 0.2

to about 06 part of sulfonating agent per part of sulfonatable petroleum fraction,

(3) adding to'the sulfonation mass of step (2):

(a) from about 0.15 to about 2 parts of water per part of sulfonatable petroleum fraction, and

(b) from about 0.5 to about 1.5 parts of volatile hydrocarbon solvent per part of sulfonatable petroleum fraction,

I (4) allowing the admixture of step (3) to stratify, there- DETAILED DESCRIPTION Suitable sulfonatable petroleum fractions for use in my invention include solvent refined lubricating oil base stocks, the sulfonic acids of which have a combining weight above 600. A preferred sulfonatable petroleum fraction is a solvent-extracted, dewaxed lubricating oil base stock having a viscosity of 140 to 230 SSU at 210 F. and a viscosity index of at least 85. These refined petroleum fractions are known as bright stock in the petroleum industry. A more preferred sulfonatable petroleum fraction is a bright stock derived from Mid-Continent base oil and having a viscosity index of at least 90'.

Any of the bright stocks which are commercially available are suitable for use in the process of my invention. 7

The preferred sulfonating agent for use in my process is oleum (or fuming sulfuric acid), with oleum containing 20 to 23 percent free 80;, being more preferred.

A suitable amount of sulfonating agent is from about 0.2 to about 0.6 part by weight per part of sulfonatable petroleum fraction. On the same basis the preferred amount of sulfonating agent is from about 0.3 to about 0.5 part. Interestingly, I have found that increasing the ratio of sulfonating agent to hydrocarbon increases the yield but results in a decrease in combining weight of the resulting sulfonic acid. This effect is shown in the 'table below.

G. sulfonic Combining Oleum/bright stock acid/100 g. weight as ratio bright stock acid The sulfonation of the petroleum fraction can be done in a conventional manner. If desired, sulfonation of the petroleum fraction can be done in the presence of a volatile hydrocarbon solvent, as defined hereinbelow. When a low molecular weight sulfonic acid is used, as described hereinbelow, if desired, a low molecular weight aromatic compound can be added to the admixture of petroleum fraction and volatile hydrocarbon solvent prior to sulfonation.

gives an emulsion problem and use of the volatile hydro: A

carbon solvent alone results in a product having a large amount of sulfuric acid. The details of the sludge-removal step will be discussed below. a

The amount of water which is added to the sulfonation mass is from about 0.25 to about 1 part by weight per part of sulfonatable petroleum fraction. The preferred amount of water is dependent on the settling temperature. At ambient temperatures (i.e., 20-25 C.) the preferred amount is about 0.5 part. However, at elevated temperatures the preferred amount isabout 0.25 part.

Suitable volatile hydrocarbon solvents include saturated low molecular weight hydrocarbons and petroleum fractions comprising these hydrocarbons, such as hexane, petroleum naphtha, Stoddard solvent, and the like. Of

these, hexane is the preferred solvent. A typical plant hexane has an API gravity of 67, an initial boiling point of 167 F. and an end point of 220 F. The volatile hydrocarbon solvent is substantially inert but can containsmall amounts (less than 2 percent) of low molecular weight aromatic compounds as described hereinbelow.

A suitable amount of the volatile hydrocarbon solvent is from about 0.75 to about 3 parts by weight per part of sulfonatable petroleum fraction. Since I have found that better results are obtained using about 1 part, this amount of volatile hydrocarbon solvent is preferred.

In order to obtain a good split between the sludge and sulfonic acid phases, it is necessaryto allow the admixture of sulfonation mass, water and volatile hydrocarbon solvent to settle for a period of time. Knowing this, anyone skilled in this art can determine the optimum, or necessary, settling time. I have found that a settling time of 12 to 18 hours is usually suflicient to enable a satisfactory split to form. The settling can be conducted at ambient temperatures. Generally, it is better .to maintain the admixture at a slightly elevated temperature, in the range of 40 to 55 C., during the settling period.

Interestingly, I have found that the addition of a low molecular weight sulfonic acid to the admixture of sulfonation mass, water and volatile hydrocarbon solvent provides a pronounced improvement in the manner of forming, a split between the sludge phase and sulfonic acid phase. As stated above, in the absence of the low molecular weight sulfonic acid, the use of heat improves the separation. Using the low molecular weight sulfonic acid, 'and'with no additional heat, I have found that a good split occurs in from 2 to 3 hours. I.

The amount of low molecular weight sulfonic acid which is used suitably is from about 1 to about 10 percent by weight, preferably from about 2 to about 4 percent by weight, based on the sulfonatable petroleum fraction.

The low molecular Weight sulfonic acid can be derived from a variety of aromatic compounds, such as benzene, toluene, xylene, mono-C C -alkylbenz'ene, mono-C C alkyltoluene, di-C -C -alkylbenzenes and the dl-Cz-Cf' alkylbenzene. The primary requisite is that theresulting sulfonic acids have a sufficiently low molecular weight that it is water-soluble. The preformed low molecular I weight sulfonic acid can be added to the mixture of sulfonation mass, water and volatile hydrocarbon solvent. If desired, the low molecular weight sulfonic acid can be formed in situ by adding the low'molecular weight aromatic compound to the petroleum fraction prior to sulmass prior to adding the water.

- separation and decreases the amount of sludge.

Upon conversion of the sulfonic acid to a hyperbasic sulfonate the presence of the low molecular weight sulfonic acid appears to have a very slight negative effect when the hyperbasic sulfonate is employed in severe applications. For this reason, when the product resulting from my process is ultimately to be used in severe applications it is preferable that the process not use the low molecular weight sulfonic acid. When the product resulting from my process is not to be used in severe applica- -"tions, because of the decreased time required for phase separation it is preferable that the process use the low molecular weight sulfonic acid.

There are many uses for the sulfonic acids produced by the process of my invention. Upon conversion to the metal salt, such as calcium, barium, magnesium, or zinc,

they can be used as a lubricating oil additive, marine diesel lubricant additive, grease additive and fuel additive. The

and calcium sulfonates, which products are particularly useful as additives in lubricating oil.

EXAMPLE 1 This example illustrates the processof my invention using technical grade n-hexane as the diluent in the recoyery of the high molecular weight sulfonic acids.

Materials used: Parts Bright stock 1 200 Oleum (20-23 S =0.3/ l oleum/ bright stock 60 n-Hexane (Phillips technical grade) 200 De-ionized water 50 A solvent-extracted, dewaxed lubricating oil base stock, having a viscosity of 156 SSU at 210 F. and a. viscosity index of 91.

Procedure: The bright stock was added to a l-liter, creased flask. Employing agitation, the oleum was added over a 2 /2 minute period. During addition of the oleum, the temperature of the sulfonation mass rose from 23 C. to 47 C. Employing a hot water bath to maintain the temperature at 5560 C. the sulfonation mass was stirred for 30 minutes. The flask was removed from the water bath and the n-hexane was added; the admixture was stirred for 5 minutes. The water was then added over a 2-minute period. During the water addition the temperature rose from 38 C. to 52 C. The reaction mass was divided into two portions and placed in separatory funnels. One portion was settled at ambient temperature while the other portion was settled in a 50 C. steam oven.

A portion amounting to 234 parts was settled at ambient temperature. At the end of 6 hours, no split (separation of sludge phase) had occurred. After overnight settling, a split had formed. Twelve parts of very thick sludge was removed. There were 3 parts of holdup in the funnel. The amount of hexane phase was 221.5 parts; it was a dark brown color and not clear.

A portion amounting to 268 parts was settled in a 50 C. steam oven. At the end of 6 hoursa small split had occurred. After overnight settling a split had occurred. An aqueous phase (49.5 parts) was removed; this phase contained some emulsion and solid material. There were 1.5 parts of holdup in the funnel. The amount of hexane phase was 2l1 parts; the hexane phase was much darker and clearer than the material settled at ambient temperature.

EXAMPLE 2 This example illustrates the process of my invention using plant hexane, which contained a small amount of low molecular weight aromatic compounds, as the diluent in the recovery of the high molecular weight sulfonic acids.

Procedure: The bright stock was added to a 12-liter, creased flask equipped with a mechanical stirrer, thermometer, and reflux condenser. The oleum was added to" the flask over a -minute period. After addition of the oleum, the reaction mass was stirred for 30 minutes while adding the low molecular weight aromatic compound to maintaining the temperature at 5560 C, by means of a hot water bath. The reaction flask was removed from the hot water bath. The de-ionizedwater'was' 'a sulfonation mass over a 7-minute period. During the water addition, the temperature of the reaction mass rose 20 C. and the mass became more viscous. Upon completion of the water addition, the reaction mass was stirred 5 minutes, whereupon the hexane was added. Upon completion of the hexane addition, the reaction mass was stirred 10 minutes.

The reaction mass was settled overnight in a 50 C. steam-oven. A clean split was obtained. A clear aqueous phase was obtained which amounted to 754 parts and containing 49.3% sulfuric acid. (The aqueous phase contained 99% of the unreacted sulfuric acid and essentially nosulfonic acid.)

The hexane phase amounted to 3695 parts and had the following analysis:

Total acidity meq./g 0.300 Sulfonic acidity meq./g 0.242 Water percent" 1.36 Combining weight (as acid) 751 The hexane phase contained the following:

Parts Sulfonic acid 671.5 Unsulfonated oil 1200.0 Sulfuric acid 10.5

Water 50.25 Hexane 1762.75

EXAMPLE 3 This example illustrates the process of my invention wherein the bright stock is sulfonated in the presence of hexane which contains a small amount of low molecular weight aromatic compounds.

Materials used: Parts Bright stock (same as in Example 1) 200 Hexane (same as Example 2) 200 Oleum (2023% S0 50 De-ionized water Procedure: The bright stock and hexane were added to a 1-liter creased flask, equipped with a mechanical utes. Thecontents of the reaction flask were transferred to a separatory funnel and allowed to settle at ambient temperature. After 2 hours, the aqueous phase had 'subst-antially separated. Phase separation was complete after settling overnight.

The aqueous phase amounted to 144 parts and had the following analysis:

Meq./g. Total acidity 6.393 Sulfonic acidity 0.001

'The hexane phase amounted to 416.9 parts and had the 7 following analysis:

Meq./ g. Total acidity 0.309 0.223

Sulfonic acidity EXAMPLE 4 This example illustrates the process of my invention employing a low molecular weight sulfonic acid. The low molecular weight sulfonic acid was formed in situ by the bright stock being sulfonated.

The procedure employed was substantially the same as inExample 1 and the bright stock was the same as in ewe -i:

The aromatic compound was benzene with 5, 2- /2, 1, and weight percent being used in the various runs.

The runs employing 2% and percent benzene gave excellent phase separation at ambient temperature in less than 1 hour. A good phase separation was obtained in about 1 hour at ambient temperature with the run employing 1 percent; however, a sludge formed at the interface. With the run employing no benzene and settling at ambient temperature, about 36 hours was required to obtain a good phase split.

EXAMPLE 5 This example was similar to that of Example 1 with the exception that p-toluene sulfonic acid was added to the water. The use of 2 and 4 weight percent of the p-toluene sulfonic acid resulted in fast phase separation at ambient temperature.

EXAMPLE 6 The procedure of Examples 1 and 2 was repeated using commercially available bright stock from various source. In all instances the source of the bright stock had no effect on the process.

EXAMPLE 7 A hexane solution of a high molecular weight sulfonic acid prepared from the same bright stock and using the procedure of Example 2 was purified by blowing with nitrogen gas and treating with lime. The purified sulfonic acid was then converted to a hyperbasic calcium sulfonate using the procedure of US. Pat. No. 3,150,088.

A SAE 10W-30 grade lubricating oil blend was prepared which contained 10 weight percent of hyperbasic calcium sulfonate.

The lubricating oil blend was tested in a double length Sequence V test (which is a standard test for MS rating of a lubricating oil). To provide a comparison, a similar blend containing 7.6 weight percent of a commercially available bright stock sulfonate was tested. (While the percentage amounts were different, the oils were blended to contain the same percent active sulfonate.)

The results of the tests are shown below, with oil A" referring to the blend containing commercial sulfonate and oil B referring to the blend containing the sulfonate prepared from the sulfonic acid prepared by my process.

Percent Piston Total Total Oil ring Oil screen Test, hours varnish varmsh sludge plugging plugging OilA" 0ilB While particular embodiments of the invention have been described, it will be understood, of course, that the fonating agent to one part of a sulfonatable pe troleum fraction, characterized as being a solventextracted, dewaxed lubricating base stock having a 8 viscosity of from about 140 to about 230 SSU at 210 F. and a viscosity index of at least 85,

(2) adding to the sulfonation mass of step (1):

'(a) about 0.15 to about 3 parts of water per part of said sulfonatable petroleum fraction, and (b) about 0.5 to about 1.5 parts of volatile, saturated hydrocarbon solvent per part of sulfonatable petroleum fraction,

(3) adding to the admixture of step (2) from about 1 to about 10 weight percent, based on said sulfonatable petroleum fraction, of a low molecular weight, water soluble, sulfonic acid,

(4) allowing the admixture of step (3) to form an aqueous phase and a hydrocarbon phase,

(5) withdrawing the aqueous phase, and

(6) thereupon obtaining a hydrocarbon solution of the desired sulfonic acids.

2. The process of claim 1 wherein the low molecular weight, water soluble, sulfonic acid of step (3) is obtained by the sulfonation of a low molecular weight aromatic compound selected from the group consisting of benzene, toluene, xylene, mono-C -c -alkylbenzenes, mono-c -C -alkyltoluenes, and di-C C alkylbenzenes.

3. The process of claim 2 wherein the sulfonating agent is oleum.

4. The process of claim 3 wherein the amount of water is from about 0.25 to about 0.50 part per part of sulfonatable petroleum fraction.

5. The process of claim 4 wherein the volatile hydrocarbon solvent is hexane.

6. The process of claim 5 wherein the amount of volatile hydrocarbon solvent is from about 0.9 to about 1.1 parts per part of sulfonatable petroleum fraction.

7. The process of claim 3 wherein in step (2) the water is added to the sulfonation mass prior to adding the volatile hydrocarbon solvent.

8. A process for preparing high-purity natural sulfonic acids, comprising the steps of:

(1) forming an admixture comprising from about to about 99 weight percent sulfonatable petroleum fraction, characterized as being a solvent-treated, dewaxed lubricating base stock having a viscosity of from about to about 230 SSU at 210 F. and a viscosity index of at least 85, and from about 1 to about 10 weight percent low molecular weight aromatic hydrocarbon compounds,

(2) adding to the admixture of step (1) from about 0.2 to about 0.6 part of sulfonating agent per part of sulfonatable petroleum fraction,

(3) adding to the sulfonation mass of step (2):

(a) from about 0.15 to about 3 parts of water per part of sulfonatable petroleum fraction, and (b) from about 0.5 to about 1.5 parts of volatile,

saturated hydrocarbon solvent per part of sulfonatable petroleum fraction,

(4) allowing the admixture of step (3) to stratify,

thereby forming an aqueous phase and a hydrocarbon phase,

(5) withdrawing the aqueous phase, and

(6) thereupon obtaining a hydrocarbon solution of the desired sulfonic acids,

said process being characterized further in that in step (2) said low molecular weight aromatic hydrocarbon compounds are converted to water soluble sulfonic acids by said sulfonating agents.

9. The process of claim 8 wherein the sulfonating agent is oleum.

10. The process of claim 9 wherein the amount of water is from about 0.25 to about 0.50 part per part of sulfonatable petroleum fraction.

11. The process of claim 10 wherein the volatile hydrocarbon solvent is hexane.

12. The process of claim 11 wherein the amount of volatile hydrocarbon solvent is from about 0.9 to about 1.1 parts per part of sulfonatable petroleum fraction.

13. The process of claim 8 wherein the low molecular weight aromatic compound is selected from the group consisting of benzene, toluene, xylene, mono-C -C -alkylbenzenes, mono-c C -alkyltoluenes, and di-C C -alkylbenzenes.

14. The process of claim 9 wherein the low molecular weight aromatic compound is selected from the group consisting of benzene, toluene, xylene, mono-C -C '-a1ky1- benzenes, mono-c -C -alkyltoluenes, and di-C 'C -alkylbenzenes.

15. The process of claim 12 wherein the low molecular weight aromatic compound is selected from the group consisting of benzene, toluene, xylene, mono-C -C -alkyl- 1O benzenes, mono-C C -alkyltoluenes, and di-C C -a1kylbenzenes.

References Cited UNITED STATES PATENTS 2,809,209 10/1957 Voorhees 260-504 2,882,301 4/ 1959 Sias et a1. 260-505 LEON ZITVER, Primary Examiner 10 A. SIEGEL, Assistant Examiner US. Cl. X.R. 260505 '13, 505 S 

